Sagån is a river in Sweden. 70 kilometres (43 mi) in length, it flows south through the municipalities of Enköping, Västerås and Sala. Its source is Doften, a lake in Heby Municipality. It flows south into Mälaren, Svealand, the third-largest freshwater lake in Sweden. Its tributaries are Lillån, Isätrabäcken and Lillån.